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0. HENKER. APPARATUS FOR TESTING LENS SYSTEMS.

APPLICATION FILED MAY23| I914.

- Patented June 3,1919.

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ASSIGNOR TO THE amnion CARL ZEISS, or JENA,

GERMANY.

OTTO HENKER, OF JENA, GERMANY,

APPTUS FOR TESTING LENS SYSTEMS.

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sary, after having ascertained the intersectional distance, to take into account the constant corresponding to the said collec- To all whom it may concern: Be it known that I, O'r'ro Hnr KER, a citizen of the German Empire, residing at Jena,

Germany, have invented a new and useful the auxiliary system or to mark a stale Apparatus for Testing Lens Systems, of fitted directly to the apparatus with suitwhich the following is a specification. able numerals. For ascertaining the posi- The invention relates to an apparatus for tion of the image of the sighting mark the testing lens systems, this collective term comuse of an ocular is to be recommended, with prising not only systems of more than one Wh1ch the Image of the mark is observed 10 member, but single lenses as well. The apand focused sharply. In order to obtain a paratus is intended to be used for experilarge measuring range and the considerable mentally measuring or testing the'so called ocular extension necessary under such cirintersectional distance of lens systems... As is oumstances, a terrestrial ocular or a microwell known, the term intersectional distance scope-will be employed. Furthermore the 1 denotes the distance of a focus from the end employment of an ocular results in a simsurface of the system facing it; hence, the plified manipulation of the apparatus, if a intersectional distance is equal to the focal scale, which is fitted to the apparatus and distance of the system only for lenses, the is graduated directly according to intersecthickness of which is infinitesimal, while for tional distances (or their reciprocals, i. e. 20 lenses of finite thickness and for all systems according to so-called vertex refractions) of 7 5 of more than one member intersectional disthe lens systems to be examined, be reflected tance and focal distance are difierent. It with the aid of a reflecting device in the is, therefore, frequently necessary or desirfield of view of the ocular, so that, while able in practice, to be able to measure and the image-plane of the sighting mark is be- 25 test the intersectional distance of a lens ing focused, the intersectional distance besystem in a simple manner. Thisis imporlonging to. it may at the same time be tant, for instance, when choosing the spec read ofi. tacle glass required for an abnormal eye, In order to keep the lens system in its as in the case of spectacle glasses the interplace, while a measurement is being made,

30 sectional distance forms an important de-. it will be given besides the vertex stop a terminingfactor, as soon as the thickness lateral support as well, which will preferof the glass is no longer infinitesimal. ably be arranged to adapt itself by spring For ascertaining the intersectional disaction to the curvature of the end surface tance the image of an infinitely distant of the system. For spherical bounding sur- 35 sighting mark which may be presented in faces a cylindrical sleeve may, for instance, the simplest manner by a collimator, will be used, which is disposed concentrically be formed by the lens system to be examined, with the vertex stop, is guided in the direcand thereupon the distance between the fotion of the sighting axis and is pressed cus lying in the image-plane and the end against the lens system by means of a heli- 40 surface of the system facing it will be meascal spring, so that the sleeve will be in contact all around, when the system is in the proper position. When the lens system has a twofold symmetrical end surface, 6. g. a cylindrical or a torio one, the system will be 7 preferably supported in four points by four yielding pins, of which each two pins lying symmetrically to the vertex stop are coupled together and are guided in such a manner that their connecting line is always perpendicular to that of the other two pins.

ured. According to the invention an apparatus intended for this purpose may be given a particularly simple and suitable form by a fixed stop being provided, against which the vertex of the lens system to be examined is to be placed, so that the distance of the-vertex from the locus of the image formed and by this means the intersectional distance may be measured.

In order to be able to determine the inter sectional distance of negative lens systems as well, an additional collective lens system of greater power will be employed, which system is preferably formed as a fixed part of the apparatus. It is then'only neces- The lens system must then, on being placed in the apparatus, be displaced or rotated about its axis, until all four pins contact simultaneously with the end surface.

The accurate settlng of an ocular or of a translucent screen to the image-locus of the sighting mark is simplified by a well-known i able with such systems to set the two focal lines one after the other without a rota tion of the diaphragm, the latter will be symmetrical termmed. Flgure 1 is a preferably provided with four holes, which are disposed in such a manner that the connecting lines of twoopposite hole centers each pass through the sighting axis and are approximately perpendicular to one another. On placing the lens system-to be tested in thehapparatus, care'must then be taken, that eac approximately in the direction of one of t e two principal planes of the lens system. In the annexed drawing a constructional example ofthe invention is shown,'in which for the sake of convenience in the manipulation of the apparatus the optical axis is de flected about in the middle of the apparatus through 90 by a reflecting prism. The apparatus is so sectional distance of systems-with twofold longitudinal section through the whole apparatus, F ig. 2 shows the planview of the supporting device for, the lens system to be examined, Fig. 3 is a cross-section through the apparatus along line 3- 3 of Fig. 1 and F ig. 4 a detail'of the apparatus.

A stand a supports on a lateral arm 5 a l casing c, which 1n its turn hontains a col The sighting mark a? of the colwhich is on a mark-carrier c is illuminated byan electric incandescent lamp there are provided two stand a. lens system to-be examined, which system is o and 0*; Behind the lens 0* and in its mount 0 there is aslot shaped recess 0, into which is inserted a diaphragm 03 having four holes. he measuring apparatus proper is'inclosed in a tubular casing e, which is fixedat its left-hand The supporting device. for the indicated in the drawing in dotted lines by a lens I, is built 1 into the said tube end. Across a'cylindri'cal sleeve 9, in the direction of-a diameter of the same, is a bridge 9 to the'center of which isfixed a point 9 which forms the'fixedvertex' stop for the lens 7. For the lateral support of the lens I cylindrical guidepieces '5 and 7:, which are concentric with the sleeve mediate sleeve it. Each' of these pieces is provided, at the top guide with two by means of a two opposite hole centers come to liedownward with constructed that the inter-.

end surfaces may also be de-.

the field of view end in a socket a on the an image of its 9 and are separated by an inter-- aeoaeeo equally high, oppositely positioned points 2, 2' and ,70 respectively and ispressed helical spring land m re spectively in the direction of the axis upwardly agalnst the lens f.. An outer sleeve in, to which the intermediate sleeve 7a and the inner sleeve 9 are fixed, serves for jour naling the whole supporting device in the socket al The guide-piece 2' is provided with a screw '5 which slides in a straight slot. 9 of the fixed sleeve 9 parallel to the axis, so that the points i and i of the guidepiece 2' may always move in a straight line parallel to the sighting axis. The same object isattained for the guide-piece k by a screw 73 which is fixed to the said piece, and a corresponding slot in the sleeve n, the various parts being so arranged that the connecting line of two corresponding points is perpendicular to that of the other two points. On placing the lens to be tested on the apparatus, the lens must be pressed turned, until it rests simultaneously both on the vertex stop and on all four supporting points.

A reflecting prism o abuts on the lower end of the sleeve 9, which prism transmits the ray pencils to a collective system p, which is fixed within the apparatus. the prism o and the system ;0 are'fixed to a cylindrical piece g, 'wh ich. closes the casing e.- F or observing andfocusing the image the hand and be shifted or of, the sighting mark, produced by the lens 1 f and the system 12, there is provided a terrestrial'ocular formed of four lano-convex lenses 7', 1' 1' and r'flthe containing tube set which is-gu-ided in two rings 6 and e fixed tothe casing e. The movement of the ocular is effected by means of a rack 8 through a pinion s and a milleddisk' 8?. A reflecting prism t is fixed by means of a ringt at the front end of the ocular and refleets a scale u, plate a and is lighted from without, into of theocular. o for reading off the scale u is fitt'ed in the image-plane of the ocular, lying between the two lenses 1' and 1", to a mark-carrier 0.

I claim:

1. Apparatus for testing comprising a collimatqr adapted. to present sighting mark, a collective I the apparatus, which. is along with the,lens system system fixed to adapted to form to be tested a' real image of the said image, a-terrestrial ocular adapted for ascertaining said'real image and supportlng means for the lens system to be a fixed stop adapted to vertex of the said lens.

the position of the' tested, comprising contact with the system.

which is fitted to a glassv The mark I lens systems, i

2. Apparatus for testing lens systemshav- I ing on the side to be examined a twofold symmetrical surface, comprising acollimator adapted to present an image of its sighting mark, acollective system fixed to the apparatus, which is adapted to form along with the lens system to be tested a real image of the said image, and supporting means for the lens system to be testechcomprising a fixed stop and four yieldingly journaled pins surrounding the said-stop, which are coupled together in diametrically opposite pairs with symmetrically disposed members and are so guided that the connecting lines of such pairs, which pass through the axis of the fixed stop, are always perpendicular to each other, the fixed stop bemg adapted to contact-with the vertex of the lens system to be tested.

3. Apparatus for testing astigmatic lens systems. comprising a collimator adapted to present an image of its sighting mark, a. collective system fixed to the apparatus, which is adapted to form along with the lens system to be tested a real image of the said image,v a diaphragm provided with four holes and adapted to be introduced into the pat-h of the rays in front of the lens system to be tested. and supporting means for the lens system to be tested, comprising a fixed stop adapted to contact with the vertex of the said lens system.

' OTTO HENKER.

Witnesses: 1

PAUL KRUGER, RICHARD HAHN. 

